High demand for raw materials and ever increasing production volumes associated with processing raw materials, as well as involvement into industrial production of raw materials having low concentration of the useful ingredients and high percentage of abrasive inclusions require that the flow-through portions of centrifugal pumps susceptible to abrasive wear should have a longer service life. Centrifugal forces cause separation of solid abrasive particles in the flow-through passage of the impeller resulting in fast non-uniform wear of inner surface of the carrying disk, vanes, and peripheral wall of the discharge passage.
Leading companies in the field of pump construction, such as "Warman", "Worthington", "Humboldt" and others attempt to increase the service life of centrifugal pumps by using new wear-resistant materials and by improving the technology involved in fabrication of elements of the flow-through portion. However, developments along these lines are extensive, and therefore an increase in the pump service life never exceeds 30-50%.
In the Soviet Union the problem of extending the service life of centrifugal pumps for handling liquids containing solid abrasive inclusions is solved both by making use of new wear resistant materials and improving procedures and techniques associated with fabrication of elements of the pump flow-through portion, and by designing new variations in the geometry of the flow-through passages. For example, there is known an impeller of a centrifugal pump for handling liquids carrying solid abrasive inclusions (cf., SU, A, No. 769,095). A centrifugal pump provided with this known impeller and tried by the "Serlachius" company has shown an impeller service life three times the service life of the pump impeller fabricated by this company.
When pumping a kimberlit pulp the impeller according to SU, A, No. 769,095 served 2-2.5 times longer than the mass-produced impellers of conventional geometry; whereas during pumping an iron ore pulp the increase in the impeller service life amounted to a factor of 3.5.
Also worth mentioning are improvements of the "Warman" company with respect to variations in the conventional geometry of the flow-through portion of the impeller and discharge passage.
There is further known a centrifugal pump for handling liquids containing solid abrasive inclusions (cf. AU, A, No. 2,528,16).
In this known centrifugal pump construction the flow-through portion is defined by a discharge passage and a flow-through passages of the impeller disposed in the housing of the pump. The impeller has a carrying disk mounted in a cantilever fashion on a drive shaft with vanes attached by their side edges to the carrying disk, other side edges of the vanes being secured to a driven disk. The discharge passage is confined by two side walls, front and rear relative to the incoming flow, and by a peripheral wall made integral with the front and rear walls. The peripheral wall has in the meridional section of the housing of the pump casing two curvilinear portions each connected with a rectilinear portion located in the middle of the peripheral wall of the discharge passage. The curvilinear portions are pocket projections, and are integrated with the front and rear walls of the discharge passage, respectively. The carrying and driven disks of the impeller are crimped accordingly toward the rear and front walls of the discharge passage. A discharge vane edge of each vane of the impeller is curvilinear, having a concavity facing the rectilinear portion of the peripheral wall of the discharge passage.
The heretofore described construction of the pump provides such a flow of liquid containing abrasive inclusions which results in reduced hydraulic losses during the travel of the liquid in the discharge passage and consequently in more efficient operation of the pump.
However, such an arrangement of the flow-through portion of the pump limits the range of application to highly dispersed abrasive mixtures. When this known pump is used for handling liquids containing solid abrasive inclusions sizing over 2 mm, the discharge passage is liable to failure due to fast wear of its peripheral wall. When pumping liquids containing large-size abrasive inclusions, the latter tend to penetrate the pocket in the zone of the rear wall of the discharge passage to accumulate therein and cause local damage to the surface of the casing of the discharge passage due to vigorous contact therewith.